The number of kilocalories in a food indicates the amount of

The number of kilocalories in a food indicates the amount of energy present in the food.
Kilocalories are the units of energy present in foods. The number of kilocalories in foods is determined using calorimetry techniques in which the food is burned and the amount of heat transfer is measured. 1000 calories is equivalent to 1 kilocalorie. Calories are contained in essential macronutrients such as protein, carbohydrates and fat. Carbohydrates and protein contains 4 calories per gram, while fat contains 9 calories per gram.

Ithink the answer is d.

Gay-lussac's law i think.